SMART people use intentional "missed calls" as a FREE messaging system.
It's a kind of "social code" that allows informal communication between known people that previously have agreed HOW and WHAT the “missed call” mean.
Suddenly, we had a BRIGHT IDEA;
"why not to use "missed calls" to develop a full, functional, normalized mobile messaging system?"
Let's think...
To make the system work, we can divide the time a "missed call” is ringing into small periods, assigning one different message to every period...
This way, we'll be able to send as many different messages as periods we can get...
OK, we can have a pre-defined message list to send...

And once you receive a message you can select your answer from another message list, like in a usual conversation...
"let's chat!"
"OK, see you in FB"

And as you send different messages to different people you can have as many message lists as contacts...
.